耗散粒子动力学模拟方法在软物质体系研究中的一些进展与应用

软物质是指处于固体和理想流体之间的复杂态物质,主要包括聚合物、表面活性剂、液晶、胶体悬浮液、以及生物大分子等。软物质能够对外界微小的作用产生强烈的非线性响应,并展现出丰富的有序自组装相态。作为一种新颖的模拟技术,耗散粒子动力学方法非常适合在介观尺度上对软物质体系的复杂行为进行合理的描述。本文对耗散粒子动力学模拟方法的发展及一些应用进行了系统评述。耗散粒子动力学模拟方法体现了分子动力学与格子Boltzmann模型的优点,通过与其它理论模型（如Flory-Huggins理论、Smoothed particle hydrodynamics模型等）相结合,该方法能够在介观尺度上有效地研究聚合物熔体和溶液体系、生物膜及囊泡体系以及胶体悬浮液等体系的行为。这些研究结果,对新材料的研发、特殊材料的制备、以及材料加工条件的选择具有十分重要的科学意义和实际应用价值。     

凝聚态物理学中的基本概念

本文首先根据物质世界的层次化来说明凝聚态物理学在当今物理学中所处的地位,并阐述了复杂与简单的辨证关系,来说明为何这一学科至今仍然富有生命力;进而对这一学科的范围进行了讨论,强调了位形空间和动量空间中都存在多种类型的凝聚现象,而相应的凝聚体构成了这一学科的研究对象;还探讨了处理凝聚态理论问题的量子物理与经典物理方法有效领域的界限与分野;最终对此学科的发展历史进行回顾,并追溯和剖析了其概念全系的演变,     

Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond

We review recent developments in the physics of ultracold atomic and molecular gases in optical lattices. Such systems are nearly perfect realisations of various kinds of Hubbard models, and as such may very well serve to mimic condensed matter phenomena. We show how these systems may be employed as quantum simulators to answer some challenging open questions of condensed matter, and even high energy physics. After a short presentation of the models and the methods of treatment of such systems, we discuss in detail, which challenges of condensed matter physics can be addressed with (i) disordered ultracold lattice gases, (ii) frustrated ultracold gases, (iii) spinor lattice gases, (iv) lattice gases in “artificial” magnetic fields, and, last but not least, (v) quantum information processing in lattice gases. For completeness, also some recent progress related to the above topics with trapped cold gases will be discussed.

Motto:     

Connections between quantum chromodynamics and condensed matter physics

Features of QCD can be seen qualitatively in certain condensed matter systems. Recently some of the analyses that originated in condensed matter physics have found applications in QCD. Using examples we discuss some of the connections between the two fields and show how progress can be made by exploiting this connection. Some of the challenges that remain in the two fields are quite similar. We argue that recent algorithmic developments call for optimism in both fields.     

Hierarchical order of Galilei and Lorentz invariance in the structure of matter

The structure of matter shows a hierarchical order: (1) from Lorentz invariance in high-energy physics; (2) to Galilei invariance in the low-energy nonrelativistic limit of high-energy physics; and (3) again to Lorentz invariance in condensed matter physics (where the velocity of sound takes the place of the velocity of light). The hierarchical order can be continued downward further to: (4) non-relativistic (velocity small compared to the velocity of sound) condensed matter excitons, obeying Galilei invariance; and (5) to excitonic matter obeying Lorentz invariance with an excitonic matter sound velocity. It was previously conjectured that Lorentz invariance of high-energy physics is preceded by Galilei invariance at the Planck scale. Still further, the conjectured Galilei invariance at the Planck scale may be the result of an underlying five-dimensional non-Euclidean conform invariant metric structure, with three spatial and two time dimensions, compactified onto three spatial and one time dimension.     

Statics and dynamics of single DNA molecules confined in nanochannels

The successful design of nanofluidic devices for the manipulation of biopolymers requires an understanding of how the predictions of soft condensed matter physics scale with device dimensions. Here we present measurements of DNA extended in nanochannels and show that below a critical width roughly twice the persistence length there is a crossover in the polymer physics.     

Higgs type excitations in cold atom systems

Higgs type excitations are the excitations which give mass to particles. The Higgs type excitations has a critical role both in particle physics and condensed matter physics. In particle physics, the suspected Higgs boson has been found by the Large Hadron Collider (LHC) in 2012. In condensed matter physics, the Higgs type excitations relate to order phase of the system. In this review, we present an overview of recent studies on the Higgs type excitations both in non-interacting and interacting cold atom systems. First, in non-interacting cold atom system, by synthesizing artificial non-Abelian gauge potential, we demonstrate that when a non-Abelian gauge potential is reduced to Abelian potential, the Abelian part constructs spin-orbit coupling, and the non-Abelian part emerges Higgs excitations. Secondly, the Higgs excitations which are the reputed Higgs amplitude mode in interacting cold atom system are discussed. We review the theoretical model and the experimental detection of Higgs amplitude mode in two dimensional superfluid. The observation of both Higgs type excitations in real experiments are also discussed.     

中子散射技术及其应用

热中子的波长和凝聚态物质的原子／分子间距具有相同的量级，而其能量又和原子／分子的热运动能量相近．因此，利用热中子的弹性和非弹性散射效应，可以从微观层次上获取物质的结构和动力学知识。目前，中子散射技术在物理、化学、化工、生物和材料科学等研究领域的应用已经获得了许多用其他方法无法得到的知识，文章介绍了中子散射的基本原理和特点，并列举了中子散射技术在相关研究领域中的典型应用     

趋向统一发展的团簇科学

团簇科学在发展过程中，从原子核物理、凝聚态物理和量子化学等引入许多概念和方法，构成团簇研究的中心议题，逐渐形成一门介于原子分子物理和凝聚态物理之间的交叉学科．文章就团簇结构和性质研究的某些最新进展进行了评述，并与原子核和量子点等的性质进行了比较．     

Spin crossover: the quantum phase transition induced by high pressure

The relationship is established between the Berry phase and spin crossover in condensed matter physics induced by high pressure. It is shown that the geometric phase has topological origin and can be considered as the order parameter for such transition.     

Baryon fluctuations from the QCD phase transition

Extraordinary baryon fluctuations can signal a nearly first order phase transition at RHIC. We discuss how these fluctuations can be measured. Next, we apply a dissipative-hydrodynamic formulation used in condensed matter physics to simulate the formation_— though spinodal decomposition_— and subsequent evolution of these fluctuations.     

凝聚态物理与量子力学

文章扼要地回顾了量子力学在奠定凝聚态物理基础中所起的关键作用;并讨论了当今凝聚态物理发展的主要动向;进而阐明了为何凝聚态物理,不论在基础研究,还是促进技术发展,抑或推动学科交叉方面,尚大有可为。     

物质结构的概念的统一性

尽管凝聚态物理、核物理和高能物理学的研究对象各不相同,它们的基本概念都是相通的。本文的目的,是从统一的观点来说明物理学的这些分支中的根本问题。希望这不仅有助于从一致的角度来理解各个领域,并且说明物理思想的沟通和借鉴,对于物理学的发展是重要的。     

Superfluid analogies of cosmological phenomena

In a modern viewpoint relativistic quantum field theory is an emergent phenomenon arising in the low-energy corner of the physical fermionic vacuum – the medium, whose nature remains unknown. The same phenomenon occurs in condensed matter systems: In the extreme limit of low-energy condensed matter systems of special universality class acquire all the symmetries, which we know today in high-energy physics: Lorentz invariance, gauge invariance, general covariance, etc. The chiral fermions as well as gauge bosons and gravity field arise as fermionic and bosonic collective modes of the system. Inhomogeneous states of the condensed matter ground state – vacuum – induce nontrivial effective metrics of the space, where the free quasiparticles move along geodesics. This conceptual similarity between condensed matter and the quantum vacuum allows us to simulate many phenomena in high-energy physics and cosmology, including the axial anomaly, baryoproduction and magnetogenesis, event horizon and Hawking radiation, cosmological constant and rotating vacuum, etc., probing these phenomena in ultra-low-temperature superfluid helium, atomic Bose condensates and superconductors. Some of the experiments have been already conducted.     

从液晶显示到液晶生物膜理论：软凝聚态物理在交叉学科发展中的创新机遇

世界之交,物理学正在与化学、材料科学、生命科学等相互交叉形成新的学科,凝聚态物理为例,在传统的固体物理以外,最近几年又诞生了一门新学科－－软件体物理、或称为复杂流体,液晶 物质凝聚态的重要研究对象,６０年代发展起来的液晶显示技术与７０年代创立的液晶生物膜理论,充分显示了软凝聚态物理在２１世纪的信息与生命科学时代将发挥重要的基础学科作用,是科学技术富于创新发展的领域。     

q-Gaussian representation of non-Lorentzian Mössbauer lineshapes

Generalized statistical physics (non-extensive/Tsallis) is being extensively used to study anomalous results in condensed matter physics. Mössbauer line shapes for systems like proteins and glasses show non-Lorentzian behaviour. In this paper we show q-Gaussian distribution can be used to represent non Lorentzian Mössbauer line shapes where q is non-extensivity index.     

Solitons in condensed matter: A paradigm

For this new journal dealing with nonlinear phenomena we review the setting of several important current problems in the physics of condensed matter (solids, liquids). We show how the concepts embodied in the mathematical analysis of solitons provide systematic new insight (i.e., a paradigm) into a central question: what are the important physical configurations in nonlinear condensed systems? Following these general issues we summarize the analysis of the dynamics and equilibrium thermodynamics (i.e., statistical mechanics) of non-linear one-dimensional model systems, and we indicate how the solitonic configurational phenomenology provides a basis for dynamic effects which are seen both experimentally and in molecular dynamics computer simulations. Many problems in condensed matter differ from the more familiar nonlinear mechanical or hydrodynamic applications in that finite temperature thermal fluctuations must be considered along with systematic dynamics.     

The cold atom Hubbard toolbox

We review recent theoretical advances in cold atom physics concentrating on strongly correlated cold atoms in optical lattices. We discuss recently developed quantum optical tools for manipulating atoms and show how they can be used to realize a wide range of many body Hamiltonians. Then, we describe connections and differences to condensed matter physics and present applications in the fields of quantum computing and quantum simulations. Finally, we explain how defects and atomic quantum dots can be introduced in a controlled way in optical lattice systems.     

Graphene-like physics in optical lattices

Graphene has attracted enormous attention over the past years in condensed matter physics. The most interesting feature of graphene is that its low-energy excitations are relativistic Dirac fermions. Such feature is the origin of many topological properties in graphene-like physics. On the other hand, ultracold quantum gas trapped in an optical lattice has become a unique setting for quantum simulation of condensed matter physics. Here, we mainly review our recent work on quantum simulation of graphene-like physics with ultracold atoms trapped in a honeycomb or square optical lattice, including the simulation of Dirac fermions and quantum Hall effect with and without Landau levels. We also present the related experimental advances.